PROJECT SUMMARY/ABSTRACT Morbidity rates for invasive colorectal cancer continue to be a major public health problem in the United States. Although targeted treatment regimens such as antibody and small molecule-based drugs exist, no current therapy effectively protects against late-stage disease in patients. Immunotherapeutic intervention holds enormous potential for eliciting specific immunity against tumor spread while surmounting treatment-associated morbidities. Unfortunately, despite advancements in countering immunosuppression and triggering potent reactivity toward self-antigens, immune-based strategies have not impacted disease progression to date. Colon cancer tends to display a considerable degree of genomic intra-/inter-heterogeneity, limiting a given strategy?s eligibility in patients and long-term therapeutic index. With respect to cancer immunotherapy, the eventual outgrowth of tumor cell variants expressing altered immunophenotypes may help explain the lack of sustained anti-tumor responses observed clinically for locally advanced and metastatic disease. An alternative and potentially improved immunotherapeutic approach involves abrogating tumor angiogenesis by initiating T cell destruction against the supportive vasculature. Conceptually, as tumor-derived blood vessel function is critical to tumorigenesis, vascular immune targets would be less amenable to therapy-induced escape and cancer relapse. The overall objectives of this proposal are to identify unique CD8+ T cell HLA-A2+ restricted stromal targets that potentiate therapeutic protection (and maintenance of subclinical disease) against colon carcinoma growth under first-/second-line treatment scenarios in clinically relevant pre-clinical models. Additionally, we intend to demonstrate prevention of colon cancer recurrence following a novel synergistically timed immunotherapeutic regimen that incorporates cytotoxicity against both vascular and cancer cells. Our central hypothesis is that anti-stromal CD8+ T cells prevent recurrence and achieve durable cancer protection by mitigating angiogenesis within the TME. The following specific aims will test our central hypothesis and appraise the successful completion of the proposal?s objectives: Aim 1 ? Test the hypothesis that anti-vascular CD8+ T cell responses induce therapeutic protection against colon carcinoma; Aim 2 ? Test the hypothesis that anti- vascular immunity prevents therapy-induced escape and synergizes with a colon cancer-specific antibody drug conjugate. Overall, our mechanistic studies will provide a clearer perspective for engaging anti-stromal CD8+ T cells as the TME proceeds through operational phases of immunotherapy-related sensitivity, dormancy, and escape. Our research efforts will also led to the characterization of protective stromal-associated peptide/HLA targets and a co-applied targeting platform, which will help spearhead the development of relevant immunotherapeutic strategies for ultimate clinical trial evaluation in patients with colon cancer. Additionally, as the blood vessel system is conserved, our experience with these unique peptide/HLA targets will have therapeutic implications for other vascularized solid cancers.